1. Field of the Invention
The present invention relates to a drying apparatus and method for drying a semiconductor wafer after being cleaned.
2. Description of the Related Art
There are various methods for drying semiconductor wafers after being cleaned using a cleaning solution.
In a spin-drying method for drying a plurality of semiconductor wafers by rotating the plurality of semiconductor wafers at a high speed, a problem arises in that the larger the diameter of each semiconductor wafer, the larger the size of the drying apparatus, and the more expensive the cost of the drying apparatus.
In order to avoid the above problem, there is proposed a method for drying semiconductor wafers using isopropyl alcohol (IPA). One example of such a method is disclosed in U.S. Pat. No. 5,653,045.
According to the technique disclosed in U.S. Pat. No. 5,653,045, target semiconductor wafers to be dried are soaked in pure water which is stored in a tank. After this, the IPA is jetted into the tank, thereby to form a thin IPA film on the surface of the pure water.
Thereafter, the semiconductor wafers are taken out from the pure water at a low speed. At the time when the semiconductor wafers pass the IPA film, the moisture on the surface of each semiconductor wafer is removed as a result of a Marangoni-flow effect.
When to take out the semiconductor wafers from the pure water, the concentration of the IPA is high around each of the semiconductor wafers and is low away from each of the semiconductor wafers. That is, the surface tension of the IPA is low around each of the semiconductor wafers and high away from each of the semiconductor wafers. In the circumstances where there is a difference in the levels of the surface tension, Marangoni flow occurs.
Kazumi Asada et al. reports, in xe2x80x9cA New Economical Wafer Drying Technology with High Process Performancexe2x80x9d, IEEE International Symposium on Semiconductor Manufacturing Conference Proceedings, (1997), that, in the drying method applying a Marangoni-flow effect, a striped pattern of particles is formed on the surface of each of the semiconductor wafers, as shown in FIG. 8.
Such particles interfere with formation of wiring having a predetermined pattern, and causes a short circuit in the wiring forming on each semiconductor wafer. In such context, a problem is that the yield and reliability of those parts to be manufactured using the semiconductor wafer, which has been dried using the method with the Marangoni-flow effect, are low.
The entire contents of the above publication and reference are incorporated herein by reference.
It is accordingly an object of the present invention to provide a drying apparatus and method for drying a semiconductor wafer while preventing particles from being adhered onto the semiconductor wafer.
In order to achieve the above object, according to the first aspect of the present invention, there is provided a drying apparatus comprising:
a tank which stores a drying liquid for drying a target semiconductor wafer to be dried;
a holder which holds the semiconductor wafer, perpendicular to a surface of the drying liquid;
a dryer which soaks the semiconductor wafer in the drying liquid, and takes out the semiconductor wafer from the drying liquid, thereby to dry the semiconductor wafer; and
a divider which divides the surface of the drying liquid on each side of the semiconductor wafer, thereby to protect an impurity removed from the semiconductor wafer to be adhered again onto the semiconductor wafer.
According to this invention, the semiconductor wafer can be dried, while particles are prevented from being adhered onto the semiconductor wafer.
The dryer may lift and lower the holder, thereby to soak and takes out the semiconductor wafer in and from the drying liquid.
The dryer may lift the holder at a rate in a range from 1 to 3 mm/min.
The divider may include a plurality of plates, each of which is formed of polytetrafluoroethylene, for dividing the surface of the drying liquid.
The dryer may discharge the drying liquid from the tank so as to take out the semiconductor wafer from the drying liquid; and
the divider may float on the drying liquid, and may move downward along with a downward movement of the surface of the drying liquid.
The divider may comprise at least one plate for dividing the surface of the drying liquid and a holding member for holding the at least one plate; and
the holding member may have such specific gravity that a top end of the at least one plate protrudes from the drying liquid.
The dryer may include a valve for adjusting a discharge amount of the drying liquid to be discharged, and lower the surface of the drying liquid at a rate in a range from 1 to 3 mm/min.
The at least one plate may be formed of polytetrafluoroethylene.
In order to achieve the above object, according to the second aspect of the present invention, there is provided a method for drying an object, comprising:
soaking a semiconductor wafer, perpendicular to a surface of a drying liquid, in the drying liquid which is stored in a tank and for drying the semiconductor wafer;
drying the semiconductor wafer by taking out the semiconductor wafer from the drying liquid; and
preventing particles, which are removed once from the semiconductor wafer, from being again adhered onto the semiconductor wafer, by dividing the surface of the drying liquid at each side of the semiconductor wafer when to take out the semiconductor wafer from the drying liquid.
The drying may include taking out the semiconductor wafer from the drying liquid by lifting the semiconductor wafer.
The drying may include lifting the semiconductor wafer at a rate in a range from 1 to 3 mm/min.
The drying may include taking out the semiconductor wafer from the drying liquid, by discharging the drying liquid from the tank; and
the preventing may include dividing the surface of the drying liquid with using at least one plate, which moves downward along with a downward movement of the surface of the drying liquid.
The drying may include lowering the surface of the drying liquid at a range in a range from 1 to 3 mm/min, by adjusting a discharge amount of the drying liquid.